Heretofore a European patent application 0 362 921 (SKF) described a bearing equipped with a sealing device mounted between two rows of balls and between the orifices arranged on the outer race and the orifices arranged on the inner race of the bearing, to allow for the passage of a fluid through the bearing. This bearing serves to establish communication between two vessels containing a pressurized fluid. The sealing device provides for the passage of the fluid through the bearing and also prevents the lubricant of the bearing, such as grease, from penetrating into the fluid passages in the bearing. However, the structure of such a device comprises many components which create substantial axial bulkiness, which may be incompatible with certain applications. Furthermore, the construction of such a device is relatively costly due to the number of distinct components that must be manufactured and assembled.
A routine application of this technique is designed for the monitoring and control of the pressure of the tires of a vehicle, the sealing device for the fluid passage being mounted in the bearings of the vehicle's wheel. Heretofore, in this particular application, U.S. Pat. No. 4,844,138 describes a device for the passage of air in a bearing comprising seals formed of a magnetic fluid which cooperates with magnetic rings to guarantee airtightness. Such a device is too sophisticated to be used in economic conditions compatible with mass production, as in the automotive field.
Heretofore, there have also been other devices for the passage of air through wheel hubs using a pair of seals to guarantee the tight passage of air between the rotating and fixed portions of the hub (see for example, European patent applications 0 204 085 and 0 208 540). The shape and arrangement of these seals in pairs creates a substantial axial bulkiness that is incompatible with certain applications and increases the cost of manufacture and installation of the device. Furthermore, the use of two distinct seals implies an effective system of axial immobilization of said seals, at the risk of their being displaced axially under the effect of the fluid pressure.